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]]>Thu, 01 Nov 2018 12:00:00 GMThttps://www.materialstoday.com/optical-materials/features/witec-raman-microscope/Plasma-assisted alignment in the fabrication of microchannel-array-based in-tube solid-phase microextraction microchips packed with TiO2 nanoparticles for phosphopeptide analysishttps://www.materialstoday.com/amorphous/features/plasmaassisted-alignment-fabrication/
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Phosphorylatedpeptides are important for understanding the processes of biological regulation. However, the detection of phosphopeptides remains a challenge because of their low abundance and the suppression by non-phosphopeptides. Here, we report a strategy for the facile and rapid fabrication of TiO2-nanoparticle-packed microchannel-array glass microchips (TMA-microchips) for in-tube solid-phase microextraction (IT-SPME) using a plasma-assisted method for the precise alignment of the microstructure. This proposed strategy was applied to the selective enrichment of phosphopeptides from a protein digestion mixture, demonstrating the high capacity and selectivity of the SPME microchips. An important feature of this array design is that it fully exploits the advantage of nanoparticles for improving extraction capacity and simultaneously provides an effective way to reduce the pressure for driving solutions; thus, it paves the way for future methods that simultaneously take advantage of nanomaterials and microchips.

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This article originally appeared inAnalytica Chimica Acta1018, 2018, Pages 70-77.

Silver nanoparticles (Ag NPs) tarnish easily upon exposure to ambient air, and eventually lose their ability as a plasmonic sensor via weakened localized surface plasmon resonance(LSPR). We have demonstrated the enhancement in plasmonic sensitivity of tarnished Ag NP aggregates to vapors of volatile organic compounds (VOCs) such as ethanol and butanol by Ar plasma exposure. The response of Ag NP aggregates to the VOC vapors was examined by measuring the change in optical extinction spectra before and after exposure to the vapors. The sensitivity of Ag NP aggregates decreased gradually when stored in ambient air. The performance of tarnished Ag NPs for ethanol sensing was recovered by exposure to argon (Ar) plasma for 15 s. The reduction from oxidized Ag to metallic one was recognized, while morphological change was hardly noticeable after the plasma exposure. We conclude, therefore, that a compositional change rather than a morphological change occurred on Ag NP surfaces enhances the sensing ability of tarnished Ag NP aggregates to the VOC vapors.

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This article originally appeared in Applied Surface Science 427 Part A, 2018, Pages 848-853.

As for practical application, ultrathin two-dimension (2D) materials have exhibited high performances in photocatalysis, electrocatalysis, and supercapacitors. Usually, when used 2D TiO2 (B) nanosheet as a photocatalyst, it absorbs only ultraviolet light, and several approaches have been taken to narrow the band gap of TiO2. Thus, we demonstrated a facile and environmental friendly method to enhancing hydrogen production by introducing defects of O vacancy and Ti3+ in surface and bulk TiO2 (B) nanosheets through the ambient-temperature plasma engraving treatment. After plasma treatment, the band gap of the 2D TiO2 (B) nanosheets decreased from approximately 3.13?eV–2.88?eV and the H2 evolution performance of them is almost twice as high as pristine TiO2 (B) nanosheets under AM 1.5 illumination. The enhanced photocatalytic performances arise from the doping defect of O vacancy and Ti3+, narrowing the energy band gap and increasing more active sites of material surface with function of plasma engraving. The findings in this work may provide a new approach for improving the photocatalytic activities of other metal oxides.

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Equivalent crystal theory (ECT) is a semi-empirical technique used for the calculation of defect energetics in metals and semiconductors. The implementation of the method involves the solution of transcendental equations. Although this is not a problem for simple defects, for complex defects, Monte Carlo and molecular dynamics calculations in large systems, it could be the speed-determining limitation in a calculation. In this paper we propose a procedure for bypassing this step and obtaining the desired result directly. The form of the particular transcendental equations suggest a different approach, namely, the equation can be cast in the form of the Lambert function that can be readily evaluated from standard routines. We test this scheme by evaluating the surface energies for a variety of metallic elements and by standard numerical approaches, and demonstrate that they agree to within a few ppm.

This article originally appeared in Computational Materials Science 42, 2008, Pages 659-663

We present our results of design of a new model of fullerite-based material with ultrahigh mechanical stiffness closely related with experimental data. In this study, we investigated the nature of enhanced mechanical characteristics (i.e. bulk modulus) and establish the relation between geometrical parameters of the model, which allows the estimations of potential conditions for fabrication of superhard material with outstanding mechanical properties. The atomic structure of proposed fullerite-based nanocomposite was analyzed and mechanical properties as a functions of geometrical characteristics were examined in details.

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]]>Thu, 18 May 2017 15:30:00 GMThttps://www.materialstoday.com/computation-theory/features/fullerite-nanocomposites-with-ultrahigh-stiffness/Surface modification of polyelectrolyte multilayers by high radio frequency air plasma treatmenthttps://www.materialstoday.com/computation-theory/features/surface-modification-of-polyelectrolyte/
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Low-temperature plasma treatments are used to perform surface modification on polymers, aiming to improve the surface properties according to the desired application. In this work, polyelectrolyte multilayers (PEMs), built by layer-by-layer deposition technique, were treated using high frequency low-temperature air plasma.

We evaluated the effect of the exposure time (20 and 300 s) and its effects on PEMs with two different top layers: alginate and carboxymethylcellulose. Chitosan was used as the cationic polymer to build the LbL films with the oppositely charged anionic polymers, alginate and carboxymethylcellulose. Our results showed that the surface topology, wettability and free charges within layers are highly correlated to the polymer pair used. PEMs of the chitosan/alginate system are thinner and hydrophilic, and present a surface with wider peaks. We found that plasma treatment promotes substantial changes on the PEMs and that 20 s of exposure time is enough to perform these changes.

In all cases, after plasma treatment, PEMs’ thickness and free charge distribution were reduced and wettability was enhanced.

This article originally appeared in Applied Surface Science329, 2015, Pages 287-291.

DNA has been used as a material for the construction of complex nanostructures. Branched DNA molecules can be glued together by sticky end cohesion, providing a route to dictate hierarchical self-assembly of one-, two- and three-dimensional periodic lattices.

DNA tiles provide site-specific attachment sites, and can lead to spatially positioned arrays of nanoparticles or macromolecules with nanometer-scale precision. This review discusses the origin and use of various DNA tiles in constructing higher order DNA lattices that can be used as scaffolds for hosting external guests. In addition, the development of DNA origami tiles and arrays is also discussed.

This article originally appeared in Applied Materials Today2, 2016, Pages 7–16.

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Near-Field Radiative Heat Transfer across Nanometer Vacuum Gaps provides an in-depth description of fundamentals and application of near-field radiative heat transfer. When the vacuum gap between two media is on the order of nanometers, heat transfer can exceed that between blackbodies. This book investigates near-field heat transfer between different materials and geometries highlighting interplay between optics, material thermophysical properties and electromagnetism. The book also highlights the application of near-field thermal radiation in the field of power generation, imaging, and thermal systems as an analog of electronic devices.

The book provides a detailed study of the principles, experiments, and industry applications of near-field radiative heat transfer, comprehensively covering both parallel and nonparallel surfaces.

Academics and industry researchers in the field of near-field radiative heat transfer. Graduate students in physics, optics, electrical engineering and mechanical engineering.

Key Features

Brings together research in near-field radiative heat transfer in a focused and comprehensive manner, allowing those new to the topic to gain a thorough understanding of the science and how it can be used

Offers focused coverage of heat transfer in near-field radiation, which other books do not

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]]>Thu, 28 Jul 2016 15:15:00 GMThttps://www.materialstoday.com/nanomaterials/features/nearfield-radiative-heat-transfer-across-nanometer/Hydrogen diffusion in ultrafine-grained palladium: Roles of dislocations and grain boundarieshttps://www.materialstoday.com/amorphous/features/hydrogen-diffusion-in-ultrafinegrained-palladium/
Diffusion behavior of hydrogen in ultrafine-grained palladium (Pd) is investigated by electrochemical permeation tests. The ultrafine-grained structure is produced by severe plastic deformation through high-pressure torsion (HPT). The diffusion behavior is compared with an annealed state with a coarse-grained structure and a cold-rolled state with dislocations and subgrain structures.

Hydrogen permeation is analyzed in absorption step and desorption step at five different temperatures in the range of 15–35 °C. Hydrogen diffusion is retarded due to hydrogen trapping by dislocations. Grain boundaries act as rapid diffusion paths for hydrogen so that hydrogen diffusion is enhanced in the HPT-processed Pd samples with the ultrafine-grained structures.

This article originally appeared in Acta Materialia, 107, 2016, Pages 168–177.

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]]>Wed, 08 Jun 2016 12:00:00 GMThttps://www.materialstoday.com/amorphous/features/hydrogen-diffusion-in-ultrafinegrained-palladium/Effects of multiple hydrogen absorption/desorption cycles on the mechanical properties of the alloy system palladium/silver (wt% = 10–25)https://www.materialstoday.com/amorphous/features/effects-of-multiple-hydrogen-absorption/
Changes to the strength, hardness and ductility of a series of well-annealed palladium–silver alloys have been investigated as a function of the number of isothermal hydrogen absorption/desorption cycles the annealed alloy specimens were subjected to. The results indicate that the overwhelming majority of the changes to the mechanical properties occur as a result of the first hydrogen exposure treatment. The degree of change to the mechanical properties of the alloys has been found to be dependent on the silver content of each alloy, decreasing as the silver content increases.

This article originally appeared in Scripta Materialia, 117, 2016, Pages 6-10.

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]]>Wed, 08 Jun 2016 11:45:00 GMThttps://www.materialstoday.com/amorphous/features/effects-of-multiple-hydrogen-absorption/Dislocation/hydrogen interaction mechanisms in hydrided nanocrystalline palladium filmshttps://www.materialstoday.com/amorphous/features/dislocationhydrogen-interaction-mechanisms/
The nanoscale plasticity mechanisms activated during hydriding cycles in sputtered nanocrystalline Pd films have been investigated ex-situ using advanced transmission electron microscopy techniques. The internal stress developing within the films during hydriding has been monitored in-situ. Results showed that in Pd films hydrided to β-phase, local plasticity was mainly controlled by dislocation activity in spite of the small grain size.

Changes of the grain size distribution and the crystallographic texture have not been observed. In contrast, significant microstructural changes were not observed in Pd films hydrided to α-phase. Moreover, the effect of hydrogen loading on the nature and density of dislocations has been investigated using aberration-corrected TEM.

Surprisingly, a high density of shear type stacking faults has been observed after dehydriding, indicating a significant effect of hydrogen on the nucleation energy barriers of Shockley partial dislocations. Ab-initio calculations of the effect of hydrogen on the intrinsic stable and unstable stacking fault energies of palladium confirm the experimental observations.

This article originally appeared in Acta Materialia, 111, 2016, Pages 253–261.

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]]>Wed, 08 Jun 2016 11:45:00 GMThttps://www.materialstoday.com/amorphous/features/dislocationhydrogen-interaction-mechanisms/Influence of trap connectivity on H diffusion: Vacancy trappinghttps://www.materialstoday.com/amorphous/features/influence-of-trap-connectivity-on-h-diffusion/
A model is given for the effective diffusion of interstitial solutes in the presence of traps. It goes beyond Oriani's by taking into account, in a simple way, the connectivity between interstitial trap sites. It shows, in particular, that the typical dimension of a network of trap sites, connected by low barriers, appears squared in the diffusion coefficient. Therefore, a large precipitate can be inefficient if it offers a fast diffusion path, even if each individual trap site is deep. The model is illustrated in the case of hydrogen trapping at vacancies in Ni, using ab initio calculations for migration barriers and Kinetic Monte Carlo for validation. Trapping/detrapping kinetic parameters for “Thermal Desorption Spectra” analysis are also given.

This article originally appeared in Acta Materialia, 103, 2016, Pages 334-340.

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]]>Wed, 08 Jun 2016 11:30:00 GMThttps://www.materialstoday.com/amorphous/features/influence-of-trap-connectivity-on-h-diffusion/Overview no. 41: The interactions of composition and stress in crystalline solidshttps://www.materialstoday.com/crystalline-materials/features/overview-no-41/
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The thermodynamics of stressed crystals that can change phase and composition is examined with particular attention to hypotheses used and approximations made. Bulk and surface conditions are obtained and for each of them practical expressions are given in terms of experimentally measurable quantities. The concept of open-system elastic constants leads to the reformulation of internal elastochemical equilibrium problems into purely elastic problems, whose solutions are then used to compute the composition distribution. The atmosphere around a dislocation in a cubic crystal is one of several examples that are completely worked out. The effects of vacancies, and their equilibrium within a solid and near surfaces are critically examined and previous formulas are found to be first order approximations. Consequences of the boundary equations that govern phase changes are studied with several examples. Finally, problems connected with diffusional kinetics and diffusional creep are discussed.

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The theory of crystal growth for diffuse and for non-singular surfaces is re-examined. It is found that if a critical driving force is exceeded the surface will be able to advance normal to itself without needing steps; if this driving force is not exceeded lateral step motion is necessary. For extremely diffuse interfaces this critical driving force will be so small that any measurable driving force will exceed it. For sharp interfaces the critical driving force will be very large, and most growth will occur by lateral step motion. For most systems however the critical driving force should be accessible experimentally.

In addition the nature of a step in a diffuse interface is discussed and its energy calculated. The conditions for interface motion by classical nucleation or screw dislocation mechanisms are derived.

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The stability of a solid solution to all infinitesimal composition fluctuations is considered, taking surface tension and elastic energy into account. It is found that for infinite isotropic solids, free from imperfections the spinodal marks the limit of metastability to such fluctuations only if there is no change in molar volume with composition. Otherwise the elastic energy due to a fluctuation stabilizes the solution and alters the criterion for the limit of metastability. For an unstable solution the kinetics of decomposition are discussed and the expected mean particle size or wavelength of the most rapidly growing fluctuation is derived.

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]]>Fri, 18 Mar 2016 11:00:00 GMThttps://www.materialstoday.com/materials-chemistry/features/on-spinodal-decomposition/A new era for liquid crystal research Applications of liquid crystals in soft matter nano-, bio- and microtechnologyhttps://www.materialstoday.com/crystalline-materials/features/a-new-era-for-liquid-crystal-research/
Fig. 1. Cartoon of a nematic phase built from rod-shaped building blocks, drawn with a vertical director n.

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Liquid crystals constitute a fascinating class of soft condensed matter characterized by the counterintuitive combination of fluidity and long-range order. Today they are best known for their exceptionally successful application in flat panel displays, but they actually exhibit a plethora of unique and attractive properties that offer tremendous potential for fundamental science as well as innovative applications well beyond the realm of displays. Today this full breadth of the liquid crystalline state of matter is becoming increasingly recognized and numerous new and exciting lines of research are being opened up. We review this exciting development, focusing primarily on the physics aspects of the new research thrusts, in which liquid crystals – thermotropic as well as lyotropic – often meet other types of soft matter, such as polymers and colloidal nano- or microparticle dispersions. Because the field is of large interest also for researchers without a liquid crystal background we begin with a concise introduction to the liquid crystalline state of matter and the key concepts of the research field. We then discuss a selection of promising new directions, starting with liquid crystals for organic electronics, followed by nanotemplating and nanoparticle organization using liquid crystals, liquid crystal colloids (where the liquid crystal can constitute either the continuous phase or the disperse phase, as droplets or shells) and their potential in e.g. photonics and metamaterials, liquid crystal-functionalized polymer fibers, liquid crystal elastomer actuators, ending with a brief overview of activities focusing on liquid crystals in biology, food science and pharmacology.

This article originally appeared in Current Applied Physics 12(6), 2012, Pages 1387–1412

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]]>Fri, 29 Jan 2016 12:00:00 GMThttps://www.materialstoday.com/crystalline-materials/features/a-new-era-for-liquid-crystal-research/Glass formation and crystallisation in rapidly solidified zirconium alloyshttps://www.materialstoday.com/crystalline-materials/features/glass-formation-and-crystallisation/
Zirconium-based alloys offer an unique opportunity for studying various aspects of metallic glass, namely glass forming ability, crystallisation modes and kinetics, diffusion mechanisms and formation of glass in bulk. Thermodynamic and kinetic rationale for glass formation have been summarised in binary and ternary metalloid free amorphous alloys rich in zirconium. A comparison has been made between the microstructures of the alloys obtained under different cooling rates in order to understand the process of solidification and the process of phase selection. The different types of nucleation processes and the growth mechanisms of crystals in the undercooled melts of Zr-based glass forming alloys have been investigated. Primary, eutectic as well as polymorphic crystallisation have been observed in the alloys of this class of materials. Crystal nucleation and growth kinetics during crystallisation has been examined.

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]]>Tue, 06 Oct 2015 14:00:00 GMThttps://www.materialstoday.com/crystalline-materials/features/glass-formation-and-crystallisation/Synthesis of high-quality lanthanide oxybromides nanocrystals with single-source precursor for promising applications in cancer cells imaginghttps://www.materialstoday.com/biomaterials/features/synthesis-of-lanthanide-oxybromides-nanocrystals/
Nanocrystals of lanthanide oxybromides (LnOBrs) with low-phonon energy and high chemical stability are of particular interest for lighting and bioimaging applications. Here, for the first time, we report the synthesis of high-quality LnOBr (Ln = La, Eu, Gd, Tb) nanocrystals using the thermal decomposition of single-source precursors. Moreover, this robust and facile method can be used to synthesize optically active ultrathin EuOBr nanosheets and Eu3+-doped LaOBr nanocrystals with unique luminescence properties. Importantly, for the first time, the application of Eu3+-doped LaOBr nanocrystals in cancer cell imaging has been demonstrated.

High conductivity and extended particle contacts are required for rapid charge percolation in flowable electrodes. In this study, carbon spheres (CS) were wrapped by highly conductive reduced graphene oxide sheets (rGO) to address these issues. Various compositions of the conductive, 3D interconnected hybrid materials (rGO@CS) were synthesized by a hydrothermal method. Synergistic effects of both materials were utilized where CS served to minimize the sheet stacking for better flowability of the suspensions, and wrapped rGO sheets enabled higher conductivity for fast charge transport throughout the suspension network. When tested as flowable electrodes, the composition with a 1:2 ratio of GO to CS exhibited the highest capacitance of 200 F/g and an improved rate performance. The improved performance is attributed to the fast charge transport in the suspension network due to higher conductivity and enhanced connectivity of the active material particles. Optimized electrodes were also examined in a flow mode which yielded a capacitance of 45 F/g.